(a) Field of the Invention
The present invention relates to a display device and a method thereof. More particularly, the present invention relates to a touch sensitive display device and a method of improving touch determination.
(b) Description of the Related Art
A liquid crystal display (“LCD”) includes a pair of panels provided with pixel electrodes and a common electrode, and a liquid crystal layer with dielectric anisotropy interposed between the panels. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (“TFTs”) such that they receive display data voltages row by row. The common electrode covers the entire surface of one of the two panels and it is supplied with a common voltage.
A pixel electrode, corresponding portions of the common electrode, and corresponding portions of the liquid crystal layer form a liquid crystal capacitor that is a basic element of a pixel along with a switching element connected to the liquid crystal capacitor.
The LCD generates electric fields by applying voltages to the pixel electrodes and the common electrode, and varies the strength of the electric fields to adjust the transmittance of light passing through the liquid crystal layer to display images.
A touch screen panel is an apparatus in which a finger or a stylus contacts to write characters, to draw pictures, or to click icons to instruct a device such as a computer to execute instructions. A display device such as an LCD that includes a touch screen panel attached thereon has its own mechanism to determine whether and where a touch occurs. However, an LCD provided with a touch screen panel has a high manufacturing cost due to the cost of the touch screen panel, low productivity due to a process step for attaching the touch screen panel to the LCD, a reduction of luminance of the LCD, an increase of the thickness of the LCD, etc.
Sensors including TFTs or variable capacitors have been incorporated into display areas for displaying images in an LCD instead of employing a touch screen panel. Such sensors sense a variation of light incident on a panel or of pressure exerted on a panel to inform the LCD whether and where a touch of a user's finger, etc., occurs.
Sensing signals generated based on output signals of the sensors may be varied depending on peripheral conditions such as temperature, the degradation of the sensors, etc. In addition, the sensors may have deviations for every LCD, so the levels of the sensing signals may not be uniform. Accordingly, it may be difficult to exactly determine whether and where a touch occurs based on such sensing signals.